1. Field of the Invention
This invention relates to an ophthalmic apparatus and control method thereof.
2. Description of the Related Art
Conventionally, an ophthalmic apparatus having an automatic exposure (AE) function and/or automatic focus (AF) function has needed a dedicated AE sensor or a dedicated AF sensor, and also needed a complex switching of a light path. For instance, a light source for dedicated light-exposure detection, emitting infrared light, and a photo-detector for photometry are described in Japanese Patent Laid-Open No. 04-150831 (hereafter Ref. 1), which also describes a fundus camera that detects and measures reflected light quantity of an eye to be examined illuminated by the light source for light exposure detection using the photo-detector. Further, an ophthalmic apparatus proposed in Japanese Patent Laid-Open No. 07-016206 (hereafter Ref. 2) comprises a dedicated unit for measuring a light quantity arranged on a path divided by a member of optical separation on a path of a unit for imaging eyes.
A fundus camera proposed in Japanese Patent No. 03630908 (hereafter Ref. 3) illuminates a mark plate of focusing on which a mark is formed by an optical thin film having a wavelength characteristic for only blocking infrared light on a substrate through which both visible light and infrared light pass, projects it on a fundus of an eye to be examined, and images it using an image sensing device in an observation system. Using such a fundus camera, the mark plate image and the fundus image can be obtained by using one image sensing device in an observation system.
As described above, because the contemporary ophthalmic apparatus having AE function and/or AF function needs the dedicated AE sensor as described in Ref. 1 and Ref. 2, it becomes complicated. On the other hand, the ophthalmic apparatus proposed in Ref 2 cannot measure the light quantity when an optical viewfinder is used.
Further, the portable fundus camera proposed in Ref. 3, having an observation unit for imaging and displaying both the image of the focus mark plate projected on the fundus and the observation image of the eye to be examined, is not configured to have a finder. For this reason, it may be impossible to detect a focusing status while observing a clear tested image in an optical viewfinder.